Electrolysis process



. United States Patent ELECTROLYSIS PROCESS Richard Leonard Kronenthal, Fair Lawn, N. J., assignor to Colgate-Palmolive Company, New York, N. Y., a corporation of Delaware No Drawing. Application July 6, 1956 Serial No. 596,144

4 Claims. (Cl. 20472) This invention relates to an improved electrolysis procedure for the preparation of alcohols and unsaturated hydrocarbons from aliphatic carboxylic acid salts.-

It has previously been proposed by Kolbe to electrolyze aqueous solutions of aliphatic carboxylic acid salts to produce paraffinic hydrocarbons according to the overall equation:

Electrolysis Anode Cathode Several side reactions are known to accompany the formation of parafiins. The formation of olefins and esters are two examples thereof:

It has also been reported by Hofer and Moest that the addition of large amounts of inorganic salts to the electrolyte results in the production of alcohols according to the following equation:

The above equations depict the liberation of carbon dioxide at the anode and sodium hydroxide at the cathode. In practice, the carbon dioxide and sodium hydroxide re act to form sodium bicarbonate.

A later investigator has proposed the use of graphite anodes, the addition of about to 30% of a' water soluble aliphatic alcohol, and the use of certain selected inorganic salts in the electrolyte in order to obtain products containing an increased proportion of alcohols and olefins in relation to the proportion of paraflinic hydrocarbons formed in the Hofer-Moest reaction.

For certain purposes, such as the production of surface-active agents by sulfonation or sulfation, alcohols and olefins are very desirable products. However, the previously proposed processes for producing alcohols and olefins from aliphatic carboxylic acid salts by electrolysis have been characterized by poor yields and relatively low current efficiency, i. e., a considerable amount of electrical current is consumed in addition to that necessary for decarboxylation of the aliphatic acid. A typical cause of lowered efiiciency is electrolysis of the aqueous inorganic salt solution used as an electrolyte.

An improved process for the production of mixtures of aliphatic alcohols and olefins has now been discovered. This process is characterized by high yields, high current efiiciencies, and easy recovery of a bicarbonate salt suit- 2,857,569 Fatentecl Jan. 6, 1959 able for neutralization of further aliphatic carboxylic acid atoms having water dissolved therein. The use of aqueous ketones as an electrolyte has been found to possess unique advantages in the production of alcohols and olefins from aliphatic carboxylic acid salts.

Although the electrolyte of the present process must be essentially ketonic in nature, it must contain dissolved therein sufficient water to enter the chemical reactions occurring at the electrodes and to provide a medium of sufficient polarity to solubilize the carboxylic acid salt and thereby permit passage of electric current, e. g. at least about 2% water. On the other hand, as the-water content increases above a certain optimum value (about 5% in the case of acetone), the electrolyte becomes more aqueous in nature and the current efficiency of the system diminishes. It is preferred that the electrolyte contain no more than about 10% water (percentages are by volume). Examples of of ketones suitable for use in the present process are the lower aliphatic ketones containing up to about 4 carbon atoms, e. g. ketone.

Electrolysis is normally carried out at as high a temperature as possible, as determined by the boiling point of the solution being electrolyzed. Preferably electrolysis is carried out in apparatus fitted with refluxing means, at

a temperature about 5 C. below that at which boiling is realized by the use of the instant ketonic electrolyte is the precipitation, on formation, of the by-product bicarbonate salt. This salt, which is easily recovered by filtration, is of high purity and may be reacted with aliphatic carboxylic acids to form further salts suitable for electrolysis.

The aliphatic carboxylic acid salts employed in the instant novel process are metallic salts of saturated or unsaturated aliphatic carboxylic acids containing more than one carbon atom. These salts may be pure or in admixture, however it is essential that they have at least slight solubility in the aqueous ketone used as an electrolyte. Suitable carboxylic acid salts for carrying out the present invention include the alkali metal salts such as sodium propionate, potassium caprylate, lithium laurate, sodium myristate, potassium oleate, potassium stearate and the potassium salts of tridecanoic acid and pentadeconoic acid. The use of salts of the higher fatty acids, i. e. those containing from about 12 to 18 carbon atoms, are especially preferred because of their availability and the usefulness of the alcohols and olefins derived therefrom for sulfona tion to form surface active agents.

In carrying out the present process, it is preferred that the electrolyte initially be charged with a. greater quantity of aliphatic carboxylic acid salt than it can dissolve. Under this condition, only a small fraction of the carboxylic acid salt dissolves in the electrolyte and the remainder forms a flocculent suspension. Duringthe course of electrolysis, the suspended material gradually dissolves, replacing previously dissolved material which has been consumed by electrolysis. Also during the course of the electrolysis, a dense, heavy precipitate of bicarbonate salt settles out.

The current density to be employed in carrying out the instant process is not critical, values of from 0.001 to 0.5 amperes per square decimeter being satisfactory. Suitable electrode materials are well known to the art, comprising graphite anodes and any of a large variety of subacetone and methyl ethyl The following examples are given to additionally illustrate the nature of the invention and it will be understood that the invention is not limited thereto.

Example I A suspension of 64.0 grams (0.269 mole) of potassium laurate in 1,300 ml. of acetone and 70 ml. of water is electrolyzed between a carbon anode and a copper cathode at 50 C. with efiicient stirring. A current of 3.0 amperes (current density=0.13 ampere per square decimeter of. anode surface) is passed through thesolution for a total of 14.5 ampere hours. Throughout most of the electrolysis a potential of about volts D. C. is adequate. Toward the end of the process the required voltage rises sharply.

During the course of the electrolysis the suspended potassium laurate, which is quite fluffy in nature, entirely dissolves and a heavy bicarbonate precipitate forms. After cooling to room temperature, the resulting mixture is filtered and affords 25.5 grams of potassium bicarbonate (94.8% of theoretical based on potassium laurate), which is shown by titration to be approximately 92% pure. The filtrate is worked up by evaporating the acetone, forming an alkaline aqueous solution of the residue and then extracting the residue with diethyl ether and evaporating. The rafrinate of the ether extraction yields 0.2 gram (0.001 mole) of lauric acid. The residue left after evap- I oration of the ether is distilled, yielding 31.2 grams of a low boiling fraction and 18.0 grams of distillation residue. Subsequent analysis of these materials show the low boiling fraction to be composed of 17.9 grams (0.116 mole, 43.1%) of hendecene and 13 grams (0.076 'mole, 28.2%) of'hendecanol. Saponification of the distillation residue affords 6.2 grams (0.031 mole, 11.5%) of lauric acid, 2.2 grams (0.013 mole, 4.8%) of hendecanol and 3.3 grams (0.022 mole equivalent, 8.2%) of docosane. Percentage figures refer to theoretical yields based on potassium laurate.

The above figures account for approximately 96% of the original potassium laurate employed. Manipulative losses most probably account for the remainder. The conversion based on recoveredlauric acid is 99.6%; the current efiiciency is 99.8%. 7

Example 11 A suspension of 32.0 gms. of potassium laurate in 1,330 ml. of acetone and 70 ml. of water is heated to 50 C. A current of 3 amperes is passed through the well stirred mixture until a total of 7.9 ampere hours is consumed. The anode is a carbon plate (current density=0.125 ampere per square decimeter) around which is wound a copper wire cathode. The required potential is initially about 14 volts D. C. After approximately 85% of the total current is consumed, the cell resistance begins to increase sharply until a potential of 150 volts is incapable of causing 3 amperes of current to flow. Electric power 4 is switched off, the electrolysis mixture is cooled, and the granular bicarbonate precipitate is removed by filtration. Upon drying, the precipitate weighs 12.3 gms., titration showing it to contain 91.6% potassium bicarbonate.

The filtrate is concentrated to a volume of 500 ml. to which is added one liter of water. The mixture is extracted three times with diethyl ether and the combined extracts are washed thoroughly with water, dried over anhydrous magnesium sulfate and concentrated on the steam'bath. Distillation of the ethereal concentrate affords 13.8 gms. of material, B. P. 40-120 (1.5 mm.)

parent to those skilled in the art that further variations and modifications of this invention can be made and that equivalents can be substituted without departing from the principles and true spirit of the invention. Thus for instance, the present process may be adapted to continuousoperation, and may if desired, .be carried out in the presence of inorganic salts.

I What is claimed is:

1. An electrolysis procedure for the production of aliphatic alcohols and olefins which comprises electrolyzing an aliphatic carboxylic acid salt in an electrolyte consisting essentially of a lower aliphatic ketone ofup to about 4 carbon atoms having'dissolved therein from about 2 to about 10% water.

2. An electrolysis procedure as set forth in claim 1 wherein said ketone is acetone.

' 3. An electrolysis procedure for the production of a mixture of hendecanol and hendecene which comprises electrolyzing potassium laurate in acetone containing from about 2 to about 10% water.

4. An electrolysis procedure as set forth in claim 3 wherein said ketone has dissolved therein about 5% water.

References Cited in the file of this patent UNITED STATES PATENTS Lindsey et al. June 8. 1954 Okada et al Nov. 13, 1956 OTHER REFERENCES Electrolytic Oxidation and Reduction, Glasstone et al.;

D. Van Nostrand Co., New York (1936); pages 284486.

Electrochemistry of Organic Compounds, Lob; John Wiley and Sons, New York (1906); page83.

, Journal of the Electrochemical Society, vol. (1939);

, pages 333-350. 

1. AN ELECTROLYSIS PROCEDURE FOR THE PRODUCTION OF ALIPHATIC ALCOHOLS AND OLEFINS WHICH COMPRISES ELECTROLYZING AN ALIPHATIC CARBOXYLIC ACID SALT IN AN ELECTROLYTE CONSISTING ESSENTIALLY OF A LOWER ALIPHATIC KETONE OF UP TO ABOUT 4 CARBON ATOMS HAVING DISSOLVED THEREIN FROM ABOUT 2 TO ABOUT 10% WATER. 